Industrial lift trucks

ABSTRACT

In an industrial lift truck of the kind having a mast assembly, a load-lifting carriage mounted for sliding movement up and down the mast, and a load support carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose, the load-lifting carriage comprises a rear part mounted on the mast assembly and a front part carrying the load support, the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part. There is provided a roller which contacts an up-and-down extending surface of one of said parts at a location below said horizontal transverse axis, which roller is mounted on the other part of the lifting carriage for rotation about an up-and-down extending axis and for movement in a foreand-aft direction relatively to said other part. An hydraulic ram is provided to effect the fore-and-aft movement of the roller so as to effect tilting of the front part relatively to the rear part about said horizontal axis, the roller also acting as an antifriction support for the lower end of the front part of the carriage during the transverse movement of the front part of the carriage and the load support.

United States Patent [72] Inventor Cecil Goodacre Basingstoke, England [21] Appl. No 817,712 [22] Filed Apr. 21,1969 [45] Patented June 22, I971 [73] Assignee Lansing Bagnall Limited Basingstoke, England [32] Priority Apr. 23, 1968 [33] Great Britain [31 19 178/68 [54] INDUSTRIAL LIFT TRUCKS 8 Claims, 6 Drawing Figs.

[52] 11.8. CI 214/701, 214/730 [51] lnt.Cl B66f9/16 [50] Field of Search 214/660, 700 701, 730

[56] References Cited UNITED STATES PATENTS 2,899,093 8/1959 Morrell 214/700 3,387,731 6/1968 Gibson et a1 214/700 Primary Examiner-Robert G, Sheridan Attorney-E. T. LeGates ABSTRACT: In an industrial lift truck of the kind having a mast assembly, a load-lifting carriage mounted for sliding movement up and down the mast, and a load support carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose, the load-lifting carriage comprises a rear part mounted on the mast assembly and a front part carrying the load support, the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part. There is provided a roller which contacts an up-anddown extending surface of one of said parts at a location below said horizontal transverse axis, which roller is mounted on the other part of the lifting carriage for rotation about an up-and-down extending axis and for movement in a fore-andaft direction relatively to said other part. An hydraulic ram is provided to effect the fore-and-aft movement of the roller so as to effect tilting of the front part relatively to the rear part about said horizontal axis, the roller also acting as an antifriction support for the lower end of the front part of the carriage during the transverse movement of the front part of the carriage and the load support.

PATENTED JUN22 I971 SHEET 1 [1F 4 PATENTEU JUN22 I97! SHEET 2 UF 4 PATENTED JUN22 I971 SHEET 3 [1F 4 INDUSTRIAL LIFT TRUCKS The invention relates to industrial lift trucks of the kind having a mast assembly, a load-lifting carriage mounted for sliding movement up and down the mast, and a load support, such as a load-supporting fork, carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose.

According to the invention an industrial lift truck of the above kind has a load-lifting carriage comprising a rear part mounted on the mast assembly and a front part carrying the load support, the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part, there being provided a roller which contacts an up-anddown extending surface of one of said parts at a location below said horizontal transverse axis and which roller is mounted on the other part for rotation about an up-and-down extending axis and for movement in a fore-and-aft direction relatively to said other part, means being provided to effect said fore-and-aft movement of the roller, to effect tilting of the front part relatively to the rear part about said horizontal axis.

This arrangement has the advantage that the roller acts as an antifriction support for the lower end of the front part of the carriage during the transverse movement of the front part of the carriage and the load support.

Preferably the roller is mounted on the rear part of the carriage and contacts a rearwardly facing surface on said front part of the carriage.

Said means for effecting movement of the roller may comprise a fluid energized ram. Preferably said fluid energized ram is double acting for effecting positively both forward and rearward movement of the roller.

Preferably also the fluid energized ram is arranged substantially horizontally and transversely to the fore-and-aft direction, being connected through a linkage to said roller. For example the fluid energized ram may act on a lever which is pivotally mounted on said other part of the carriage, said roller being mounted on said lever so that pivotal movement of the lever by the ram effects movement of the roller in the fore-and-aft direction. The fluid energized ram may be connected between two levers spaced transversely apart across said other part of the carriage, each lever having mounted thereon a roller contacting said up-and-down extending surface of said one part of the carriage.

In any of the above arrangements the means for moving the load support transversely of the truck may comprise a fluid energized ram arranged horizontally adjacent the pivotal connection between the front and rear parts of the carriage and connected at each end respectively to said parts by spherical joints.

By way of example, a specific embodiment in accordance with the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic side elevation of an industrial lift truck of the kind to which the invention is applicable, FIG. 2 is a side elevation of a load-lifting carriage and load-lifting forks of an industrial truck,

FIG. 3 is a front elevation of the load-lifting carriage shown in H6. 2, the load-lifting forks being omitted;

FIG. 4 is a'plan view of the linkage provided to effect pivotal movement of the front part of the load-lifting carriage;

FIG. 5 is a section through the spherical joint 33 of FlGv 3; and

FIG. 6 is a section through the spherical joint 34 of FIG. 3.

The subject of this example is an industrial truck of the general kind shown in FIG. 1 and having a mast assembly 9 and a load-lifting carriage 12 mounted for relative sliding movement up and down the mast. Load-supporting forks 16 are carried on the load-lifting carriage. This invention is only concerned with the construction and operation of the loadlifting carriage and the load-supporting forks and thus the following description will be limited thereto.

With reference to FIGS. 2 and 3 of the drawings, the loadlifting carriage 10 has two pairs of rollers 11 mounted in the normal manner for engagement with the vertical uprights 9 of the mast assembly. The carriage 10 is also split into two parts, a rear part 12 carrying the rollers 11 and a front part 13 which has rearwardly extending brackets 14 pivotally mounted on coaxial horizontal transverse bars 15 fixed to the rear part, adjacent its upper edge. The front part may thus be pivoted relatively to the rear part, in a clockwise direction as viewed in FIG. 2, about the axis of the bars 15, into tilted position. The means provided for effecting this pivotal action are described in detail below. A pair of forks 16 are carried by the front part 13 of the carriage. These forks will thus move with the front part and may thus be tilted so that a load thereon will tend to be maintained in the heel of the forks.

The means provided for pivoting the front part of the carriage and the forks comprise a double-acting hydraulic ram 17 arranged horizontally between the rear and front parts of the carriage, and having its cylinder 18 and plunger connected at their ends, respectively, to identical lever mechanisms 20 which support rollers 21 resting against the rear surface of the front part of the carriage, adjacent its lower edge. More specifically each lever mechanism 20 (see FIGS. 2 and 4) comprises a pair of bellcrank levers 19, one above the other, connected by a boss 22 and pivotally mounted at 122 on the rear part 12 of the carriage, about a substantially vertical axis. Also one arm 23 of each lever 19 is pivotally connected in one case to the outer end of the plunger 180 of the ram 17, and in the other case to the cylinder 18, and the other arm 24 of each lever 19 is pivotally connected to the respective roller 21, the axes ofthe pivotal connections at the ends of each lever being parallel to the axis of the respective pivotal connection 122. In operation, extension of the ram 17 will cause longitudinal movement of both the plunger 180 and the cylinder 18 and hence will cause the rollers 21 to press against the rear surface of the front part 13 of the carriage and to pivot the front part of the carriage and the forks in a clockwise direction as shown in FIG. 2, about the horizontal axis of the pivot bars 15, and into their tilted positions. Also, subsequent contraction of the ram 17, i.e. the return movement of both the plunger and the cylinder, will return the rollers 21 to their initial positions and allow the front part of the carriage and the forks to be returned to their initial positions shown in FIG. 2, at a controlled rate, by means of their own weight and the weight of any load that may be present on the forks.

It is to be appreciated, however, that there is no positive connection between the lower end of the front part of the carriage and the lever mechanisms 20. This provision has the advantage that if the truck is being reversed with the load carriage close to the ground, and the front part of the load carriage and/or the forks hit an obstruction of the ground, the front part of the carriage and the forks will pivot in the abovedescribed manner to allow them to ride over the obstruction without damage to the truck. ln order that the forks cannot pivot in a manner to cause damage to the connections to a second jack described later, a stop member 40 is provided on top of the front part of the carriage. After the obstruction has been cleared, the front part of the carriage and the forks will return to their normal vertical positions.

A further feature of this embodiment comprises means provided to effect movement of the front part 13 of the carriage and the forks 16 along the aforesaid pivot bars 15 and thus transversely of the truck. These means comprise a second horizontal hydraulic ram 30, the cylinder of which is pivotally mounted on the rear part 12 of the carriage and the plunger 31 of which ram is pivotally connected to a bracket 32 extending rearwardly from the front part of the carriage. These connections include spherical joints 33 and 34 which allow the ram to swing when the front part of the carriage is pivoted, in the manner described above, about the axis of the pivot bars 15. However, to minimize the amount of movement in this direction, the ram 30 is mounted as close as possible to the pivot bars 15.

The construction of the spherical joint 33 is shown in FIG. 5. The end of the ram cylinder 30 is slotted and embraces a bracket 35 which is mounted on the rear part 12 of the lifting carriage. A pivot pin 36 passes through registering holes in the bracket and the slotted end of the cylinder. A sleeve 37 having a spherical outer surface encircles the pin 36 and seats within a corresponding shaped ring 38 mounted in the hole in the bracket 35. The spherical joint 34 is of somewhat similar construction, as shown in FIG. 6. In this case the plunger 31 has mounted at its end a slotted sleeve 39 which embraces a bracket 40 secured to the front part 13 of the lifting carriage. The other parts 36, 37 and 38 of the joint correspond to the similarly numbered parts in the joint 33.

As is clear from FIG 2, transverse movement of the front part 13 of the carriage and the forks 16 will rotate the rollers 21, whereby the rollers act as antifriction supports for the lower end of the front part of the carriage during the transverse movement thereof. The surface of each of the rollers 21 is curved to provide an even rolling action during tilting movement.

ln the embodiment described above, the lower end of the front part of the carriage is capable of being tilted forwardly to raise the forward ends of the forks. If desired, the tilting mechanism may be modified so that the front part of the carriage can also be tilted rearwardly so that the forks slope downwardly.

lclaim:

1. An industrial lift truck having: a mast assembly; a loadlifting carriage mounted for sliding movement up and down the mast; and a load support carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose; the load-lifting carriage comprising a rear part mounted on the mast assembly and a front part carrying the load support; the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part; there also being provided a roller which contacts an up-and-down and transversely extending surface of one of said parts at a location below said horizontal transverse axis; which roller is mounted on the other part for rotation about an up-and-down extending axis and for movement in a fore-and-aft direction relatively to said other part, means being provided to effect said fore-and-aft movement of the roller, to effect tilting of the front part relatively to the rear part about said horizontal transverse axis.

2. An industrial lift truck according to claim 1 wherein said roller is mounted on the rear part of the carriage and contacts a rearwardly facing surface on said front part of the carriage.

3. An industrial lift truck according to claim 1 wherein said means for effecting movement of the roller comprise a fluid energized ram.

4. An industrial lift truck according to claim 3 wherein said fluid energized ram is double acting for effecting positively both forward and rearward movement of the roller.

5. An industrial lift truck having: a mast assembly a load-lifting carriage mounted for sliding movement up-and-down the mast; and a load support carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose; the load-lifting carriage comprising a rear part mounted on the mast assembly and a front part carrying the load support; the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part; there also being provided a roller which contacts and up-and-dowri and transversely extending surface of one of said parts at a location below said horizontal transverse axis; which roller is mounted on the other part for rotation about an up-and-down extending axis and for movement in a fore-and-aft direction relatively to said other part, a fluid energized ram being provided to effect said fore-and-aft movement of said roller, to effect tilting of the front part relatively to the rear part about said horizontal transverse axis,

said ram bein arranged substantially horizontally and transversely to san fore-and-aft direction and being connected to said roller through a linkage.

6. An industrial lift truck according to claim 5 wherein the fluid energized ram acts on a lever which is pivotally mounted on said other part of the carriage, said roller being mounted on said lever so that pivotal movement of the lever by the ram effects movement of the roller in the fore-and-aft direction.

7. An industrial lift truck according to claim 6 wherein the fluid energized ram is connected between two levers spaced transversely apart across said other part of the carriage, each lever having mounted thereon a roller contacting said up-anddown and transversely extending surface of said one part of the carriage.

8. An industrial lift truck having: a mast assembly; a loadlifting carriage mounted for sliding movement up-and-down the mast: and a load support carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose; the load-lifting carriage comprising a rear part mounted on the mast assembly and a front part carrying the load support; the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part; there also being provided a roller which contacts an up-and-down and transversely extending surface of one of said parts at a location below said horizontal transverse axis; which roller is mounted on the other part for rotation about an up-and-down extending axis and for movement in a fore-and-aft direction relatively to said other part, a fluid energized ram being provided to effect said fore-and-aft movement of the roller, to effect tilting of the front part relatively to the rear part about said horizontal transverse axis, said ram being energized horizontally adjacent the pivotal connection between the front and rear parts of the carriage and connected at each end respectively to said parts by spherical joints. 

1. An industrial lift truck having: a mast assembly; a loadlifting carriage mounted for sliding movement up and down the mast; and a load support carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose; the load-lifting carriage comprising a rear part moUnted on the mast assembly and a front part carrying the load support; the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part; there also being provided a roller which contacts an up-and-down and transversely extending surface of one of said parts at a location below said horizontal transverse axis; which roller is mounted on the other part for rotation about an up-and-down extending axis and for movement in a fore-and-aft direction relatively to said other part, means being provided to effect said fore-and-aft movement of the roller, to effect tilting of the front part relatively to the rear part about said horizontal transverse axis.
 2. An industrial lift truck according to claim 1 wherein said roller is mounted on the rear part of the carriage and contacts a rearwardly facing surface on said front part of the carriage.
 3. An industrial lift truck according to claim 1 wherein said means for effecting movement of the roller comprise a fluid energized ram.
 4. An industrial lift truck according to claim 3 wherein said fluid energized ram is double acting for effecting positively both forward and rearward movement of the roller.
 5. An industrial lift truck having: a mast assembly a load-lifting carriage mounted for sliding movement up-and-down the mast; and a load support carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose; the load-lifting carriage comprising a rear part mounted on the mast assembly and a front part carrying the load support; the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part; there also being provided a roller which contacts and up-and-down and transversely extending surface of one of said parts at a location below said horizontal transverse axis; which roller is mounted on the other part for rotation about an up-and-down extending axis and for movement in a fore-and-aft direction relatively to said other part, a fluid energized ram being provided to effect said fore-and-aft movement of said roller, to effect tilting of the front part relatively to the rear part about said horizontal transverse axis, said ram being arranged substantially horizontally and transversely to said fore-and-aft direction and being connected to said roller through a linkage.
 6. An industrial lift truck according to claim 5 wherein the fluid energized ram acts on a lever which is pivotally mounted on said other part of the carriage, said roller being mounted on said lever so that pivotal movement of the lever by the ram effects movement of the roller in the fore-and-aft direction.
 7. An industrial lift truck according to claim 6 wherein the fluid energized ram is connected between two levers spaced transversely apart across said other part of the carriage, each lever having mounted thereon a roller contacting said up-and-down and transversely extending surface of said one part of the carriage.
 8. An industrial lift truck having: a mast assembly; a load-lifting carriage mounted for sliding movement up-and-down the mast: and a load support carried on the carriage, the load support being capable of being moved transversely of the truck by means provided for this purpose; the load-lifting carriage comprising a rear part mounted on the mast assembly and a front part carrying the load support; the front part being pivotally connected to the rear part to pivot about a horizontal transverse axis and being slidable together with the load support transversely of the rear part; there also being provided a roller which contacts an up-and-down and transversely extending surface of one of said parts at a location below said horizontal transverse axis; which roller is mounted on the other part for rotation about an up-and-down extending axis and for moveMent in a fore-and-aft direction relatively to said other part, a fluid energized ram being provided to effect said fore-and-aft movement of the roller, to effect tilting of the front part relatively to the rear part about said horizontal transverse axis, said ram being energized horizontally adjacent the pivotal connection between the front and rear parts of the carriage and connected at each end respectively to said parts by spherical joints. 